Slurries and suspensions of comminuted solids in an aqueous medium generally contain a dispersing agent to effectively disperse the solids. Commonly used dispersants include anionic polyelectrolytes and alkanolamines such as 2-amino-2-methyl-1-propanol (AMP.TM.). U.S. Pat. No. 4,017,324 discloses a slurry containing kaolin clay, a suspending agent and an alkanolamine dispersant. U.S. Pat. No. 4,345,945 describes an AMP.TM. phosphate salt which disperses pigments in a water based, flat wall paint. The AMP.TM. phosphate salt is prepared by mixing AMP.TM. with phosphoric acid. U.S. Pat. No. 4,370,171 also discloses an agent for dispersing pigments in a water based paint. The agent is formed from an alkanolamine and a polymeric carboxylic acid.
Monoisopropanolamine (MIPA.TM.), sold by Dow Chemical Company, is used to aid dispersion of pigments and other comminuted solids. Although MIPA.TM. is a suitable dispersant, it is a high cost material. A need exists for a lower cost dispersant that is at least as effective as MIPA.TM..
The dispersing agent of the present invention is more effective than MIPA.TM. as indicated in the dispersion performance tests for gloss development, high-shear viscosity stability, dispersion stability (seeding), while contributing to an overall reduction in yellowing. The dispersing agent is a low cost material because it contains less than 55 wt. % active material as compared to 100 wt. % MIPA.TM..